Not getting enough sleep may lead to weight gain, according to a laboratory sleep restriction study finding a big boost in calorie intake.

Action Points

This study was published as an abstract and presented at a conference. These data and conclusions should be considered to be preliminary until published in a peer-reviewed journal.

This study found that not getting enough sleep may lead to weight gain.

Note that activity didn't increase to compensate during the extra time awake.

Not getting enough sleep may lead to weight gain, according to a laboratory sleep restriction study finding a big boost in calorie intake.

Healthy individuals ate almost 550 extra calories when they missed out on an average 1 hour 20 minutes of sleep, Andrew D. Calvin, MD, MPH, of the Mayo Clinic in Rochester, Minn., and colleagues found.

But activity didn't increase to compensate during the extra time awake, the group reported at the American Heart Association's Epidemiology and Prevention/Nutrition, Physical Activity and Metabolism (EPI/NPAM) meeting in San Diego.

Those unburned calories likely "would accumulate and eventually translate into extra fat," Calvin explained in an interview with MedPage Today. "Lack of sleep probably does contribute to weight gain and obesity."

There's no magic number for sleep duration that would keep one thin, though, he cautioned.

Sleep needs vary by individual, so people should aim for what feels like enough, Calvin suggested.

"At this point our best recommendation for individuals is if they are looking to maintain a healthy weight or to lose weight, they should make sure they get enough sleep," he said.

Clinicians too need to consider sleep -- not just related to weight, but for any number of health problems, Calvin suggested.

"It is always worthwhile to ask about sleep," he told MedPage Today. "It's a simple first step."

His group's study included 17 healthy adults ages 18 to 40 who spent eight days and nights in a lab where they were free to eat whatever food they wanted, but were randomized to have their normal sleep time cut by a third, or to sleep normally.

For the sleep-deprived individuals, continuous brain wave monitoring showed that they spent only 5.2 hours asleep compared with 6.5 hours at baseline, a modest difference similar to what often happens in everyday life, the researchers noted.

The extra time awake didn't raise active energy expenditure as measured by inclinometers and accelerometers; neither group saw a significant change.

However, sleep restriction raised average calorie intake by 549 kcal per day compared with baseline; the controls actually cut their calorie intake by 143 kcal per day in the lab (P<0.01 for difference).

It's possible that people got hungry to counteract tiredness or that they simply had more opportunities to eat given the longer time spent awake, Calvin noted. But adjusting for the extra time awake with an analysis of calories-per-hours-of-wakefulness still showed a surplus in the sleep restriction group.

That suggests "there are real biologic changes that are happening because of a lack of sleep that make people eat more," Calvin pointed out.

But exactly what those impacts are remains unclear.

The researchers suspected they would see a change in hormones that regulate appetite and did find trends for increased leptin with sleep deprivation (+8.4% versus -9.8% among controls, P=0.12) and decreased ghrelin (-4.9% versus +4.6%, P=0.38). However, those shifts were the opposite of what was expected and "more consistent with a consequence of a positive energy balance than a cause," the researchers explained.

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